In semiconductor technology, due to the high mobility values, Group III-Group V (or III-V) semiconductor compounds are used to form various integrated circuit devices, such as high power field-effect transistors, high frequency transistors, and High Electron Mobility Transistors (HEMTs). A HEMT is a field effect transistor incorporating a very thin layer close to the junction between two materials with different band gaps (i.e., a heterojunction).The thin layer, instead of a doped region as is generally the case for Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), acts as the channel. In contrast with the MOSFETs, the HEMTs have a number of attractive properties including high electron mobility, the ability to transmit signals at high frequencies, etc.
The thin layer that forms the channel of a HEMT includes highly mobile conducting electrons with very high densities, giving the channel a very low resistivity. The thin layer is known as a Two-Dimensional Electron Gas (2DEG). The performance of the HEMT is closely related to the carrier density in the 2DEG, and the higher the carrier density is, the better the performance may be obtained.